Efforts to improve the effectiveness of multi-paned glazing lights, and to enhance their longevity have been directed to the provision of improved peripheral seals, to the use of humidity controlling, hygroscopic agents within the lights, and the introduction of selected, controlled atmospheres within the lights. A filling of pure noble gas such as argon, krypton or the like can improve the insulative value of the glazing unit by as much as 10%.
The virtual exclusion of oxygen by providing a 95% to 97% concentration or better, gas filling, to minimize the presence of atmospheric oxygen, substantially extends the effective life span of the glazing unit, by delaying the onset of degradation due to oxidation.
In U.S. Pat. No. 2,213,395 September 1940, Hopfield, the use is taught of a vacuum chamber for evacuating window lights, and the introduction therein of heated dried air, for purposes of minimizing the level of humidity within the light. This prior method suffers from the disadvantages that in order to achieve a high degree of control of the ultimate air filling, an unduly high level of vacuum is required, while the use of heated, dried air as the filling agent leads to a glazing light, in the cooled working condition, wherein internal pressure has not been accurately set in relation to atmospheric pressure.
Use of this prior system for purposes of filling lights with noble gases suffers from the drawbacks of:
1) requirement to pump down to an unduly high level of vacuum; PA0 2) inability to consistently fill to a high percentage purity of noble gas; PA0 3) undue amount of time to achieve unit filling; PA0 4) absence of provision to seal window lights within the protective environment of the vacuum chamber; PA0 5) somewhat large losses of noble gas to the outside environment.
A gas filling system, relying solely upon gradual displacement of air within a glazing unit, due to the greater density of the displacing gas, has been used and is unduly slow, and is further limited by the shape of the glazing light. (U.S. Pat. No. 4,369,084, January 1983 Lisec)
Thus, lights of an irregular shape may be totally unsuited to utilizing this method.
Another system, is shown in U.S. Pat. No. 3,683,974 August 1972, Stewart et al. involving the introduction of the noble or other gas as the purging and air displacement medium within a window light. This system is not consistent in the degree of purity of fill gas achieved, while requiring unduly large amounts of the fill gas, as the purging medium, being discharged to atmosphere. The defects of the system are more apparent in the case of window lights incorporating internal pane dividers or other obstructions, which act as impedances to effective purging flow. Precise control of ultimate fill pressure is difficult to achieve.